42 ELEMENTARY BIOLOGY. [CHAP. 



/ The genital glands; immediately external and 

 ventral to e. (cf. Sect. B. 2. h.) 



g. ^\\.Q pleiiro-peritoneal membrane. This will be most 

 readily seen stretching from the dorsal border of 

 the kidney to the upper angle of the body-wall; 

 having found it, proceed as under. 



a. Start from one kidney and follow it upwards ; on 

 reaching the body-wall it becomes closely applied 

 thereto, lining it, in the form of a dense pig- 

 mented membrane i^ parietal-layer or peritoneum). 



(3. Follow it downwards on the same side. It passes 

 over the outer face of the kidney and then gives 

 rise to a fold which suspends the genital gland 

 (mesorc/iium ^, mesoarium f) ; the folds of 

 . opposite sides then meet in the middle line and 

 pass down as a double membrane (mesentery) 

 which suspends and enwraps the intestine* 



Little difficulty will be found with the above, if, 

 starting from the l^idney, the membrane be care- 

 fully torn away as followed. 



y. The cisterna magna {sub-vertebral ly77iph sinus) \ 

 a spacious cavity into which the kidneys project, 

 enclosed between the folds of the mesentery 

 dorsal to the alimentary canal. The cut ends of 

 a large blood-vessel {dorsal aorta) and of certain 

 small nerves will be seen lying within it. 



2. Obliquely forwards, across the anterior end of the 

 body cavity ; to pass through the heart, the anterior 

 border of the liver and the roots of the lungs. Cf. 

 generally with i. and note in addition. 



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